Gongcheng Kexue Yu Jishu/Advanced Engineering Science

There are few in-situ creep test data of tunnel anchor for suspension bridge. To obtain the creep deformation law of tunnel anchor of Xingkang Bridge on Yakang Expressway and enrich creep test data of tunnel anchor of super-large suspension bridge, creep tests of 1∶10 in-situ shrinkage model of the Ya’an side slope tunnel anchor of Xingkang Bridge were carried out, based on the specific geological conditions in the Ya’an side slope tunnel anchorage area of Xingkang Bridge and the similar theory of elastic mechanics. According to the creep characteristics of the model anchor and surrounding rock mass under 1.0P, 3.5P and 7.0P loads, the whole creep process of the model anchor, surrounding rock and interfacial dislocation were analyzed. The results show that under 1.0P, 3.5P and 7.0P loads, the maximum creep deformation of anchor body was 0.62 mm, 0.97 mm and 1.58 mm, the maximum creep deformation of surrounding rock was 0.49 mm, 0.85 mm and 1.38 mm, and the maximum creep deformation of anchor body and surrounding rock was 0.15 mm, 0.64 mm and 1.43 mm, respectively. On the basis of in-situ scale tests, the three-dimensional viscoelastic-plastic numerical analysis of the interaction between anchorage and surrounding rock mass was carried out by using FLAC3D finite element software. The comparison between the field measured values and numerical analysis results shows that the measured creep deformation and calculation results of the anchorage and surrounding rock of the Ya’an side bank slope tunnel of Xingkang Bridge have the similar evolution trends and range of amounts. The creep of tunnel anchorage and surrounding rock mass of Xingkang Bridge on Yakang Expressway belong to stable creep stage under various loads. The long-term stability of suspension bridge was not affected by the creep of anchorage and surrounding rock mass. The test results provide a basis for the reliability evaluation of the tunnel anchorage system of Xingkang Bridge, and also provide a reference for similar engineering designs.

Volumetric error (VE) is determined by machine tool geometric error elements (GEE). Most of VE models in recent studies have a common issue that some GEE are missing in models explicit mathematical expressions, which directly affects machine tool VE prediction accuracy. Therefore, a methodology for complete modeling machine tool VE was proposed. Multi-body system theorem and homogeneous coordinate transformations were borrowed as analysis approaches. On the basis that initial positions and original errors eigen matrix were fully considered, VE model was guaranteed to have total machine tool GEE. Furthermore, aiming at the residual error limitation in traditional NC code VE compensation technique, NC code coordinates optimization design problem was described to replace the former reversal accumulation process. Genetic algorithm (GA) was then utilized to solve the proposed optimization problem so that VE compensation residual error was eliminated. A horizontal machining center was selected as study object, on which both numerical and experimental analyses were performed to verify the proposed modeling methodology and compensation technique. The results indicated that complete VE model comprises total 21 GEE of machining center and that VE prediction was fairly accurate. It was also showed that NC code optimized compensation technique presented in this paper may promote machining center volumetric position precision (VPP). The maximum growth of VPP, compared to uncompensated value, was 90.92%. Research results can be regarded as theorem and engineering supports for investigations on numerical manufacturing equipment precision problems.

To investigate the anti-seismic resilience of inter-story substructure of PEC column-steel beam frame with partial self-centering friction damped connection, a specimen with 1∶2 scale was designed and fabricated, then two tests before and after renovation were conducted under cyclic lateral loading. Based on the test observations and measurements, the specimens’ anti-seismic behaviors such as the hysteretic characteristics, lateral stiffness, self-centering function and energy-dissipation capacity were studied. The results indicated that rational dimension of bolt slotted hole was designed to achieve the force-transfer mechanism of partial self-centering friction damped connection at design-earthquake level and bearing-type connection was formed at maximum considered earthquake level; the force-transfer mode of concrete equivalent strut was formed in the panel zone due to pre-tension penetrating bolts and pre-tensioned bars, and reinforced gusset plate was designed to confine concrete in the panel zone, correspondingly the anti-seismic requirements of strong joint were met when the inter-story drift arrived at the inter-story drift limit of frame structure at design-based earthquake level, self-centering functions were sound for residual drifts of inter-story were 0.11% and 0.13%, respectively, while the inter-story drift surpassed the inter-story drift limit of frame structure at maximum considered earthquake level, self-centering functions were still good for residual drifts of inter-story were 0.42% and 0.44%, respectively; with simple repairmen, the force-transfer developing process, lateral stiffness, self-centering function and evolution mechanism of energy dissipation were restored, hence the specimen owned superior anti-seismic resilience.

With the increasing depth of underground engineering, the accurate evaluation of the depth and the degree of excavation damage zone (EDZ) in deep rock engineering is gradually influenced by the high geostress field and it is important to assess the impact reasonably. Relying on the excavation of a deep diversion tunnel, the drilling plan of distressing the in-situ stress step by step was adopted. At the outer zone of sampling area, conventional sampling holes were drilled in the form of a circular closed boundary. And boreholes and low stress coring were also carried out at the centre of the sampling area. The acoustic detection results of the depth and the degree of the damage area under different in-situ stress levels were obtained at the same location by acoustic detection device, and laboratory tests were carried out based on the core samples from the holes above. The uniaxial compressive strength of rock mass under different in-situ stress levels were given from acoustic wave velocity results by Hoek-Brown strength empirical formula to represent rock mechanics properties. These above contributed to judge the influence of the different in-situ stress levels on acoustic detection and damage degree evaluation in blasting EDZ. Researches showed that the conventional acoustic detection of excavation damage zone in high stress area would underestimate the depth of surrounding rock and the damage degree, which would be underestimated about 10% to 30% when the initial stress was 45 MPa. When the local stress level was reduced from 45 MPa to 30 MPa, the uniaxial compressive strength of rock mass would be seriously overestimated about 30% to 100%. Therefore, the high in-situ stress level had a significant impact on the results of acoustic detection and damage zone evaluation of surrounding rock. The effect of in-situ stress level on acoustic detection must be taken into account and corrected properly by reducing and increasing in evaluating rock mass quality by using wave velocity index in engineering.